Wifi signal is good but without internet

Since yesterday my internet connection keeps on dropping. I check and the wifi signal at home is good, the devices are connected on the wifi but there is no internet. It is 2 days now I cannot work and I make a hotspot with my 4g from the mobile. 

I had the same issue some months ago, but I received a notification from KPN that they fixed something in the neibourhoud and after that it was stable. Sadly enough the same problem happens again. 

I am looking forward to a quick resolution of the issue. 

P.S. I have reset the modem and the fiber with the right order as the support team suggests. Even after that I have the same problems.